1. Field of the Invention
The current invention relates to a device, in particular for a display unit.
2. Description of the Related Art
In particular with display units which find preferred application outdoors the problem arises that the display units must be cooled with the assistance of expensive cooling units in order to prevent unacceptable heating of same. This is problematic in particular if the display units are subjected outdoors to high solar irradiance. Display units may for example include displays. The displays may themselves be equipped with polarizers or may emit polarized light.
In order to prevent heating through solar irradiance, an infrared (IR)-radiation reflecting SIPLEX-solar control film which is produced as a laminated glass by Haller (Kirchlengern) is applied onto the glass, in particular onto the panel, preferably onto the front panel of the display unit. However, with a solution of this type there is still a transmission in the IR-range, in other words in the wave length range of 780 to 2000 nanometers (nm) of 28% which results in that heating through incident light radiation, in particular through solar irradiance, of a display unit which is equipped with and disposed behind such a glass panel that cannot be sufficiently avoided. For heating through solar radiation, radiation having wave lengths in the range of 700 nm to approx. 1200 nm is particularly relevant, since the solar spectrum in this wave length spectrum still possesses appreciable energy. Furthermore, a high share of radiation is absorbed by the SIPLEX-Solar-Control-Film, so that the front panel heats up considerably and transfers the heat, for example to the display positioned behind it.
Additional films which reduce heat input through external solar irradiance are, for example laminates, which include an XIR film by Southwall, Palo Alto, Calif., USA (Internet: www.southwall.com). With this film a higher share of the undesirable solar irradiance is reflected in the IR-spectral range, so that a small reduction of the radiation onto the display arranged behind it, or respectively onto the display unit, can be recognized. However, this XIR film is highly absorbent so that the front glass is heated more strongly than it would be when using the Siplex solar-control film. Moreover the XIR film is encapsulated through lamination which leads to strong optical inhomogeneity so that a practical application in the field of display glasses is not possible.
One disadvantage of the aforementioned films is that low transmission is gained with high absorption. The result is that the front panel, for example a display unit, heats up and due to the heat radiation, heat is introduced into the entire system, in this case the display unit.
An additional disadvantage of the aforementioned solutions was that the influence is restricted to the infrared spectral range, in other words to within the wave length range of 780 to 2500 nm. Especially in the visible range of 380 nm to 780 nm, however, a considerable part of the solar irradiance is effective and leads in addition to the infrared range to considerable temperature increases of the display behind a front panel of a display unit. Especially in areas of high solar irradiance this results in that heating up through incident light radiation, in particular through solar irradiance, of a display unit which is equipped with and disposed behind such a glass panel cannot be sufficiently avoided and that the display is heated to above its maximum permissible operating temperature. This causes the display to become black and it is therefore no longer legible. For heating through solar irradiance the entire spectrum with wave lengths in the range of 300 nm to approximately 2500 nm is relevant. The known solutions for reduction of solar irradiance generally only target the infrared range of 780-2500 nm in which the human eye is not sensitive and leave the visible spectral range essentially unaffected, even though solar spectrum in this wave length range still possesses appreciable energy.
Passive methods to reduce the energy being introduced into the visible wave length range are coatings which reflect a high share of the visible light, thereby reducing the incoming energy. An example for this is the product MIRONA by SCHOTT AG, which has a reflection of approximately 35% in the visible range. The disadvantage of this solution is that the contrast of the display unit disposed behind it is substantially reduced by this reflectivity. The relation of the desired radiation from the display unit to the viewer in regard to the radiation which is reflected from the surrounding area on the front side of the front panel of the display unit becomes increasingly poorer with increased ambient brightness and often leads to complete illegibility of the display unit at bright daylight. As a solution for improvement of this contrast, glass panels which are coated with anti-reflective coatings are often used in these situations which however, offer no effective solar protection in the visible range. An additional disadvantage of the films, in particular when used in a display unit was that they displayed poor optical characteristics.
A laminated glass panel having an IR-reflective layer has become known from US 2009/0237782 A1, especially for large area glass. Further, DE-A-15 96 810 shows large glass panels with a metal coating, in particular a gold or copper coating which reflects infrared radiation and long-wave light. A solar- and heat-ray reflecting laminated glass panel has also become known from DE-C-199 27 683. In addition, DE-A-195 03 510 provides a method for producing an IR-reflective laminated glass panel. Further, DE-T-694 30 986 provides a light valve as an electrode with a coating having low emission properties. Display units have also become known from DE-A-28 24 195 or JP-A-2006-162890.
What is needed in the art is a device which avoids the disadvantages of the current state of the art.